Additional information:

San Joaquin pocket mouse

Perognathus inornatus

What do they look like?

San Joaquin pocket mice have silky soft fur that doesn't have any bristles or spines. The fur on their back is pale or pinkish, with dark brown hairs on top. The fur on their bellies is white, and they have orange markings around their eyes. Their tail is longer than the rest of its body, and is two colors. San Joaquin pocket mice get their name from the fur-lined pockets in their cheeks where they store and transport seeds. Their subspecies have different body sizes, tail lengths, colors, and skull characteristics. ("San Joaquin Pocket Mouse", 2009; "Terrestrial Mammal Species of Special Concern in California", 1998; Best, 1993; Reid, 2006)

Where do they live?

San Joaquin pocket mice live in the river valleys of central California, including the San Joaquin, Sacramento, and Salinas valleys. They also live at the bottom of the western Sierra Nevada mountains and the western Mojave desert. (Hafner, et al., 1998; Linzey and Hammerson, 2009)

How do they reproduce?

During the time when females can mate, females chase, fight, sunbathe, mark territory, dig, kick, and groom themselves. Males and females probably both have more than one mate, but there isn't a lot of information available. ("San Joaquin Pocket Mouse", 2009; Best, 1993)

San Joaquin pocket mice breed from March to July. Females have at least 2 sets of 4 to 6 young every year. Females are able to mate during certain times, which usually last 5 to 6 days. ("San Joaquin Pocket Mouse", 2009; Best, 1993)

Young San Joaquin pocket mice are born in a burrow near the base of a shrub. They stay in their burrow until they mature. Females feed their young milk after they are born, so they invest a lot of effort in their young. Males probably don't contribute to caring for the young. ("Stanislaus River Report", 1995; Linzey and Hammerson, 2009)

How long do they live?

San Joaquin pocket mice have been observed living up to 10 years. Most probably live only one to a few years and most mortality probably occurs when individuals are less than 1 year old. (Reid, 2006)

San Joaquin pocket mice can live up to 10 years. Most of them probably live 1 to 3 years, and most of the deaths are before age 1. (Reid, 2006)

How do they behave?

San Joaquin pocket mice are active at night when they hunt, and spend the day underground in a burrow. Some of them will be searching for food above ground while others are inactive underground. They hibernate in phases during fall, winter, and spring, depending on how much energy they have. In the spring, they have a normal body temperature much more often than they do in winter. San Joaquin pocket mice sunbathe by digging in the ground with their forepaws, lowering their cheeks, and laying down. They switch back and forth between sides and choose their spot to sunbathe based on what others are doing. This means it may have started as a way to spread their scent. They also scent-mark on purpose. San Joaquin pocket mice can also be found gathering seeds, traveling, and making burrows or nests. ("Terrestrial Mammal Species of Special Concern in California", 1998; Best, 1993)

Home Range

Scientists haven't don't have much information about the home range of San Joaquin pocket mice.

How do they communicate with each other?

San Joaquin pocket mice communicate by growls, squawls, and low-pitched grunts. They also chatter their teeth and drum their feet. They also use scent marking and touching to communicate during mating. They have senses of sight, touch, hearing, and chemicals. (Best, 1993)

Do they cause problems?

How do they interact with us?

Are they endangered?

San Joaquin pocket mice are listed as a species of least concern on the IUCN Red List. Although agricultural and urban development have led to habitat loss, degradation, and fragmentation, they are currently considered secure throughout much of their range. Most of the population decline has been in the northern part of the range. It is thought that up to 90% of the original habitat has been destroyed. Official threats include; agriculture, annual and perennial non-timber crops, and industrial farming and ranching. Rodenticides used to control ground squirrel populations also threaten San Joaquin pocket mice. ("Terrestrial Mammal Species of Special Concern in California", 1998; Linzey and Hammerson, 2009)